Air venturi



AIR VENTURI Filed oct. 51, 1942 INVENIOR.

Patented Oct. .26, l1943 AIR VENTURI John F. Campbell, Detroit, Mich.,assigner tt George M. Holley and Earl Holley Application October 31,1942, Serial No. 464,145

1 Claim. The object of this invention is to obtain a triie pressurecorresponding. to a fair average of the velocity` of the air enteringthe carburetor.

It is and has been for about '30 years the practice to use a doubleventuri. The smaller one 'of the two discharges into the throat of thelarger one. The depression in the throat of thesmaller venturi is thusgreater than the depression in the throat of the larger and is used as ameasure of the flow of air. So long as the carburetor does not exceed100 horse power, this methodis very satisfactory. When the capacity ofthe carburetor exceeds 2000 horse power, for example. this means isinadequate. Furthermore, the dimensions of the venturi becomeunmanageable. These carburetos have to be fitted in the fuselage of anordinary airplane. The ordinary engines in use in `the air are radialand is it necessary for the carburetor to be mounted immediately to therear of the engine and to draw its air in immedi ately from the top ofthe engine and the entrance to the venturi is located immediately behindthe propeller.

I have discovered` that if I make the venturi rectangular and have thelonger side many times the shorter side, that is if I have a long narrowventuri, I can shorten the length of the venturi. I can also make thenecessary 90 degrees turn easier. However, I discovered that with a longnarrow venturi, the airilow in various parts of the venturi variesgreatly because the air behind the propeller is greatly disturbed andthe mere fact that the air makes a 90 degree turn immediately beforeentering the throat of the venturi is itselfv a cause of eddies, hencethe depression in one part of the venturi will be quite different fromthe depression in another part of the venturi. The problem was how tosample the air ilowing through the venturi so as to get a, true readingoi' the average airflow.

Fig. 1 shows a cross sectional plan view taken o n plane I-I of F18. 2.

Fig. 2 shows a cross sectional elevation taken of piane 2-2 of Fig. l.

Fig. 3 shows on smaller scale the arrangement of the venturi in the airentrance to airplane engine. l

In the iigures, the two walls of the venturi A and B are curved so. asto form a Venturi throat.

lInto this throat there discharges a venturi of smaller size formed bytwo walls which 'are letwhich is the sampling tube used for determininggv the fiow'of air through the venturi.

Operation During the operation of the plane in flight,

the eddies in the air entrance cause variations in the velocity of owthrough the small throats formed by the partitions Cil-G1, hence a fairavy erage depression is created in the tube E..

turi and arranged in line along the long axis of said larger venturi. aplurality ofpartitions in the throat of the smaller venturi, meansforming a common passage having independent connections with theindividual spaces formed by said partitions in said smaller venturi.

JOHN F. CAMPBELL.

